Process for the manufacture of globular nitrocellulose



United States Patent PROCESS FOR THE MANUFACTURE OF GLOBULAR NITROCELLULOSE Charles M. Reinhardt, St. Louis, Mo., assignor to Olin Mathiesou Chemical Corporation, East Alton, IlL, a corporation of Virginia No Drawing. Application January 12, 1955 Serial No. 481,486

'4 Claims. (Cl. 5222) g This invention relates to plastics and particularly to the manufacture of minute spheres, or near-spheres, of

the majority of the grains ina given-production batch will fall within fairly close limits (within the normal size range), such controls have definite limitations. It has notheretoforebeen possible to produce on a mass scale smaller sizes of well-formed globular grains} except to the extent that about 1%, or less, of a batch of,

normal size grains might approach a diameter of 0.002- inch. Y I Forsome years; it has been thought that the manufacture of globular powder grainshaving a diameteron the-order'of' 0.001 inch, or less, would be desirable for certain purposes, and vwhile manyeiforts have been made in: that 1 direction, they have been uniformly unsuccessful with thesole exception, so far as I- am informed, of the ently inconquerable tendency to coalescgand conse quentlyt'i'ieii-"yield' or well-formed grains of the size ap-.-

nitrocellulose, -orv the like, is' formed and dispersed in; water irrraccc'irdan'ce.with the'te'achingsfof the aforesaid patents,'and the 'sizeof the dispersedglobules is-reducedv process disclosed in tth'e copending application of 1 Eugene? A.:.Andrew, Serial.No. 470,412. While the aforesaid patents proclaim that the grain: size may" be'controll'ed byzvaryingrthervigor: of the: agitation (the more vigorous thezagitation, the. smaller theglobules) of the liquor in which the-.lacqueris suspended,- on by varyingzthViscositynofr'thedac quer (the-zhigher the. viscosity,'.the'" larger I the-figlobules'y, the :first: mentioned-mode of control "exhibits-very definitezlimitsyof opera'bility while the last mentionechmodez-of controlisierraticand uncertain; For example; using: .ar -typical' lacquer consisting. of: 3 spar-ts byzwei'ghtr of. ethyl: acetate to each part of nitrocellulose,- n i 'fll filz t-in'gi :the -agitator in a commercial production f still\-:a,t-.-.-1.6.0 r:p.m'..-.during: the grainingrstageof the procz-f; @SS, results in the production of a batchiofghardened grains, 60% of which will fall within the diameter limits of 0.016 to.0,025. inch and,;be.,near-perfect. spheres. If, other conditions remaining the same, the agitator speed is increased to-i2'30r.p:-m. idur ing theligraiiiiiig stage, 70% ofthe finishedgrains will be between 0.009. and 0.016 inch andqtbejnearertectspheres.It Tthe'f agitator speed; ,be furtherii'ncreased'to 3001;111:111; about 90% of the grains will; :be Ehetween 0:006 and 0:012 inchijn diametn'but thefincidence. of'matformatiomis greater. Further crease in agitator "speedhasno"appreciable infilll'lQQfi grain. size;

Despit f .orable"indic'ati'onswhi hj'have perenniaa no hTet'o' tinre"with"lab story. scaleibatcli'e's, theuncertainty which"attends "eifot'ts "of control grain size by varying the viscosity of the lacquer is well-known 98% by dewatering and desolventization.

.More; specifically, the invention "contemplates that iii-- trocelluloseglor the like, and a suitable solvent, such as to those who have had the experience with the manufacturef'-,of. globular-powder in commercial production stills?" The erratic and uncertain nature of. the results obtained from merely varying the viscosity of the la q er, at thesame. speed of agitation, is 'illustrated by the folld ng table which gives the; screen analysis; of the end-"product from four runs of the. same commercial still agitated at r.p.m., but at progressively increas-. ing solvent ratio (ethyl acetatemitrocellulose);- I I Solv. Ratio v on on on {on on. through 0. 3 18. 1 30; 2 17,2 21. l 12. 0.2 1.3 38.2 i 30.3 20.8 9. 0. 0 2. 9 46. 8' 23.8 16,2 10. 0.1 v 0.2 34 2 35.1 21.7 8.

Efforts to 'lc'ombine high agitation spee ds with low viscosity ia'eqfiersmv been; repeatedly made, bu t the trial batches made for this purpose have exhibited an apparproaching- 0.002 inch'in diametefhas been even lessthan the accidental yield of such grains from normal size grain .p'roduction.- I

It:.'is .-.an-1object of the present-"invention; to provide a process: forthe .mass production of near-spheres. of nitrocelliiloseandthe like, having a diameteron the order; of;.0.f00.-1 inch: or less. v

In accordance with the present'invention, a lacquer-of to the;greatesflpractical extent byboth decreasing the viscosity (-i.e., increasing the solvent content) of the" lacquer. ;and-"by increasing the rate of agitation. In

addition,'.the-invention is predicated upon the' discovery; thatfurtherureduction ini'thezultimate grain sizemay be accomplishedby emulsifying withineachlacquer globule a substantial quantity, ontheforderof 50% by volume,- of water. After the high water content lacquer globules aredispersed in the aqueous medium, they may'be'dewatered by'the techniques disclosed-inthe aforesaid patent, No. 2,160,626, and :then" solid ifie'd by removal of solvent; Upon such dewatering and desolventization,

the globules shrink to a volume-of about one-fortieth of their original size. .Consequently, if care be taken to reduce. the globules to the smallest size feasibleby the techniquesjof viscosity reduction nadvigorous agitation; the smallest size can be further reduced by upwards of ethyl acetate or a methyleth'yl ketone-toluene mixture, be-made into-a homogeneous lacquer o'fhigh-fluidity containing sayt 1.0 parts by weight of solvent to-each part of nitrocellulose; With this thin lacquer,*alarge quart-f tity of water, at least equal to,':and' preferably in excess of, the. weight' ofthe lacquer, but containing an hydrophobic surface-active agent, is mixed; The mixture is then vigorously agitated for a time"-suiiicient to thoroughlyemulsify the water. within the lacquer. .Ther e after, the water-in-lacquer emulsion is. dispersedin the; unemulsified excess of water .towhich 'is'iadded sufiicient of an hydrophilic surface-active agent. to emulsify the' water-in-lacquer emulsionvwithinthe excess oflwater so i as to produce a water in lacquer'in water-"emulsionin vvhiQhr heZ'dis ersed globuleseof'lacquercoritain pn the order of 50% by volume of water. Thereafter, the

graining, dewatering, desolventization and hardening techniques taught by the aforesaid patents may be prof2,9'19,1s11 Pat te pe 2 3 .1959

ceeded with. In view of the fact that the water content at atmospheric pressure,

of the globules accordance with the present invention is many times the water content of the globules envisionedbythe aforesaidpatents, thedewatering phase (as taught specifically by PatentNo. 2,160,626)[is'neces sarily more prolonged than inthe, practice describedin saidpatents. As a specific example of th'e process, one partby weight of nitrocellulose is formed into -a lacquer with. parts by 'weiglit ofethyl acetate. The lacquer may, if desired, contain asmall amount of a suitable stabilizer, such as 2-nitrodiphenylamine.The mixture of solvent and nitrocellulose with or without stabilizer is agitated and mixed for aboutthirty minutes, or until a homogeneous lacquer is produced. 25 parts of water containing.0.0l25 part of an hydrophobic surface-active agent, such as diethyleneglycol monolaurate, is then vigorously agitated.

with the lacquer for about an hour, emulsifying at least Up to this stage;

When the emulsification of'water intothelacquer has about half'the water into the lacquer. the process is carried out at room temperature.

been accomplished, the temperature of the batch is elevated to about40 C., at which time there is added to the mixture a solu tion consisting of: I

r I Parts: Water 1.25 Gum arabic 0.125 Sodium"dioctylsulfosuccinate ;.005

In lieu of the gum arabic, other protective colloids, .such as Belgian; gum, animal plues, or collagenous. vegetable protein, may;be utilized. In lieuof the sodium dioctylsulfosuccinate, other hydrophilic surfaceeactive agents,

such as sodium dihexylsulfosuccinate, or sodium'tetral decyl sulfate, may be utilized.

is around 70-' l2 During thistwo-hour period of temperature elevation, the water in lacquer globules are dewatered and shrunk to about 50% of their previous volume. Desolventization proceeds after the temperatureof solvent vaporization is achieved, .and in view of the high content of solvent within the globules, it is desirable that the removal thereof proceed slowly so that about six hours is allowed for its completion. Upon removal of thesolvent from the globules, they will have shrunk to less than 10% of their dewatercd volume so that when the solvent .removal is completed, and the grains are hardened, the size of the globules i-sabout 5%, or less, of their original size. The

greater the amount? of water emulsified within each individual globule, ,the smaller, will be the ultimate size of that globule. In carrying out the process as just indicated, the final product consisted of well-rounded grains having a diameter under 7.5 microns. I j

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is: ,1 1. In the manufacture of solidified globules having a diameter of 0.001 inch or less from a lacquer whose base g material is nitrocellulose,-the process comprising preparing a lacquer consisting essentially of 1 partpf nitrd cellulose and approximately 10 parts of a water-immiscible solventktherefor, agitating said lacquer with water containing a hydrophobic surface active agent until an amount of water at least equal to the weight ofthe lacquer reverses phase so. asto become the external phaseof, a watenih-lacquerein-water emulsion wherein wateriii-lacquer globules are dispersed in an aqueous external phasen Agitation iscontinued at: a rate such as to reduce th e globules of lacquer, (containing water) to the desired size, 1 Agitation speeds. of the character employed in ;a particular still for the production of normal sized globular powder, grain'slwill sufiice, but where it -is desired to produce the smallest possible sizes, the agitation,spedshould be furtherjncreased to just short of the .speed whereat malformation (due to coalescence 'of globules) becomes appreciable, it being noted in this connectionthatthe maximum tolerable speed of agitation depends upon .the idiosyncrasies ofthe particular still employed. ;-In order to-produce globular grains approach ing colloidal size,.khow.ever, care must be exercised that the globules-"of water-in-lacquercontain on the order of 50%, water after-such globules are emulsified as the internal phase of the emulsion.

Having 1 produced the water-in-lacquer-in-water emul sion with globules. of thersmallest practicable size, but

containing ontheuorder of"50% water, the globules are dewatered in. accordance with the practice taught in Pat ent Np. 2,160,626by the introduction of sodium sulfate,; or other-appropriate salt, into the aqueous external phase of thewater-imlacquer-in-water emulsion; For th1Spl11'pQS6,0.75 part of sodium sulfate dissolved in" 1.5133115. of water. may be gradually added over ape riod of:,about1thirty minutes: while the temperatureof the mixture is maintained' at 50-52 C. Atthe endof the, salt addition, the rate of heat input to the mixture is increased over a period of two hours to bring the quer is emulsified into said lacquer as the internal phase thereof, subdividing said emulsion into fine globules and suspending said globules in an aqueous bath by vigorous, agitation, andwhile so suspended: adding a water-soluble solute immiscible with the lacquer to the bath, maintaining the globules in suspension until substantially all of the, water is removed therefrom so as to shrink said glob:

ulesyand then further shrinking the globules by remova ing solvent therefrom.

2. A manufacture prepared by the process of claim 1:,comprising solidifiedglobules of nitrocellulose lacquer having a diameter of 0.001 inch or less. r

3. The process of claim lwherein the water content.

3 tate and a methyl ethyl ketone-toluene mixture, agitating said lacquer with water containing a hydrophobic surface: active agent until an amount of water at least equal to the' weight of the lacquer is emulsifiedinto said lacquer *as the internal phase thereof, subdividing the lacquer into globules and suspending them in an aqueous bath by vigorous agitation of thebath, dissolving a water soluble solute immiscible with the lacquerin the bath,

dewatering the suspended lacquer globules by maintaining the suspension of the globules in the bath containing thesolute and removing the solvent from the dewatered lacquer globules.

"ReterencesCited inthe fileiof this patent v UNITED STATES PATENTS 1,965,577 Cochran July 10, 1934 1,972,891 f Ingraham Sept. 11, 1934 2,027,114 r Olsen Jail 7, 1936 2,16 O,'626- Scha e fer- May 30, 1939 2,176,678 ,Neuroth Oct. 17, 1939 2,179,314 Allison NOV. 7, 1939 2,201,640 Weldin May 21, 1940 2,213.255 5 Olsen Sept. 3 1940 

1. IN THE MANUFACTURE OF SOLIDIFIED GLOBULES HAVING A DIAMETER OF 0.001 INCH OR LESS FROM A LACQUER WHOSE BASE MATERIAL IS NITROCELLULOSE, THE PROCESS COMPRISING PREPARING A LACQUER CONSISTING ESSENTIALLY OF 1 PART OF NITROCELLULOSE AND APPROCIMATELY 10 PARTSD OF A WATER-IMMISCIBLE SOLVENT THEREFOR, AGITATING SAID LACQUER WITH WATER CONTAINING A HYDROPHOBIC SURFACE ACTIVE AGENT UNTIL ANAMOUNT OF WATER AT LEAST EQUAL TO THE WEIGHT OF THE LACQUER IS EMULSIFIED INTO SAID LAQUER AS THE INTERNAL PHASE THEREOD SUBDIVING SAID EMULSION INTO FINE GLOBLUBLES AND SUSPENDING SAID GLOBLUES IN AN AQUEOUS BATH BY VIGOROUS AGITATION AND WHILE SO SUSPENDED: ADDING A WATER-SOLUBLE SOLUTE IMMISCIBLE WITH THE LACQUER TO THE BATH, MAINTAINING THE GLOBLUSE IN SUSPENSION UNTIL SUBSTANTIUALLY ALL OF THE WATER IS REMOVED THEREFROM SO AS TO SHRINK SAID GLOBULES, AND THEN FURTHER SHRINKING THE GLOBLUES BY REMOVING SOLVENT THEREFROM. 